I did my first AG brew Sunday. With no real clue as to how to calculate strike temperature, I went with 172 degrees for approximately 32 lbs. of grain in a 48 quart cooler. My mash temp was 149 degrees, but I was shooting for 153.
With no way to add heat to the cooler, I had no choice but to run with it. I added four ounces of Lactose to try to compensate somewhat. This is a twelve-gallon batch with a S.G. of 1.090 at 75 degrees. Does anyone know how to calculate for the lost Dextrins to replace the sweetness that should be there? Is it better to use Lactose, Malto-dextrin, or something else?

You probably would have been ok. 149 -153 not that much
Of a big deal. To me a beer this big( SG 1.090) a mash temp
Of 149 would help the beer attenuate fully and not be
To sweet. What yeast did you use and how much lactose did
You add?

I used Trip's VBIP recipe. I added four ounces of Lactose, and Safale 05. Trip doesn't know what yeast the 'meister gave him, and Yeasty doesn't remember. The recipe calls for WLP001 which always gives a funky marshmallow flavor and is too temperature sensitive, so I opted for a clean yeast instead.
I ended up with close to 13 gallons in the primary, which means I should end up with 10 1/2 to 11 gallons when it's time to keg it up. I think I still want to add some more unfermentable sugar. If it were an ordinary porter, I'd let it go, but the VBIP needs to be a little sweet to complement the vanilla.
Right now I'm trying to find whole vanilla beans. I've been to three supermarkets and Joey's. When I ask for vanilla beans, the workers look at me like I'm from Mars. I guess they think vanilla is a brown liquid that is made in a factory from coal tar or something.

I found the vanilla beans at Fresh Market, but they were way too pricey. I finally found them at Super One on sale for less than half of the price at Fresh Market. As far as ordering them online, that takes too long, I need them for the secondary, which will either be Thanksgiving day or Friday after.
At this point I need to figure out how much malto-dextrin to add to make up for my low mash temp. Any Ideas?

i think it's to late to try making up for missed mash temp.
Malto dextrin if add to the seconadry will start fermentaion again
and raise the abv. Lactose will not ferment and should add
mouth feel and a little sweetness.

I mite be wrong but I'm sure it" going to turn into a nice
beer.
dont woooooorrrrrrrrry.

Lactose (4 oz)
AD395
A unfermentable sugar used to add body and sweetness. Use 4 to 8 oz in 5 gal.

Maltodextrin (4 oz)
AD390
Good for adding mouth feel and body to extract brews without affecting flavor. Maltodextrin is added to the wort at the same time as the extracts. Maltodextrin is a chain between 4 and 20 dextrose units in length making it only 3% fermentable by brewer's yeast. It is naturally present in finished beers, up to 6% by weight. Our maltodextrin is composed of .5% dextrose, 2.5% Maltose, 3.5% maltoriose and 93.5% higher saccaharides. It is also available by the pound or even the sack. Since maltodextrins are easily digestible carbohydrates, some long range bicyclists mix maltodextrins with water as an energy source. After we learned that little fact, some of us cyclists here at Beer, Beer & More Beer are now filling are water bladders with beer. (kidding)

Ummm...careful with that, I think that maltodextrin is still about 3% fermentable....If your looking for bottle bombs, then thats the way to go....otherwise, I'd consider boiling some up and throwing it into the fermenter.

Yeah, but I want to check my F.G.first and see if I really need it. Do you know how to calculate what I'm missing? and how much the Lactose made up for? I can't seem to find out.
Anyway, 3% fermentable of one pound in twelve or so gallons wouldn't make a noticeable difference in co2 volume would it?

Okay. Final gravity was 1.020 at 75 degrees. I haven't calculated the alcohol content yet. Tasted like crap. I went ahead and put in the malto-dextrin and the bourbon, but it looks like it's headed for the sewer. $100 down the drain.